The present invention relates to a vehicle wiper device, and more particularly to a wiper device for wiping an openable rear window.
A typical station wagon or a hatchback has a rear door for opening a trunk. There are openable glass type rear doors. The glass of an openable glass type rear door can be opened independently from the rear door. A typical wiper device for wiping the window glass of an openable glass type rear door is directly attached to the window glass.
The wiper device has a relatively heavy actuator. When the window is shut, the glass may collide with the rear door. The collision applies a relatively great force to the glass where the actuator is fixed. This can damage the glass. Manually opening and closing the window requires relatively great physical force. Also, if the actuator is attached to the glass, wiring for supplying electricity to the motor in the actuator becomes complicated.
To solve the above drawbacks, a wiper device having an actuator attached to the rear door has been proposed. In this device, a wiper arm is pivotally supported by the rear window. When the rear window is closed, the wiper arm is coupled to the actuator.
FIGS. 25 and 26 illustrate such a wiper device. The device includes an actuator 101, a transmission unit 102 and a wiper arm 103.
The actuator 101 is fixed to a rear door 104. A pivot disk 106 is fixed to an output shaft 105 of the actuator 101. The pivot disk 106 is rotated within a predetermined angle range, and the direction of rotation alternates. The disk 106 has a coupler hole 106a, which is radially spaced from the axis of the output shaft 105.
The transmission unit 102 includes a shaft holder 107, which is fixed to a rear window 108, which is glass. A pivot shaft 109 is rotatably supported by the shaft holder 107. When the rear window 108 is closed as illustrated in FIG. 25, the axis of the pivot shaft 109 is aligned with the axis of the output shaft 105. The distal end of the pivot shaft 109 extends to the exterior of the rear window 108. The wiper arm 103 is fixed to the distal end of the pivot shaft 109. The distal end of the wiper arm 103 is coupled to a wiper blade (not shown). The wiper blade wipes the surface of the rear window 108.
The distal end of the pivot shaft 109 (the end extending to the actuator 101) is coupled to the crank lever 110. As shown in FIGS. 25 to 28, the distal end of the crank lever 110 is coupled to a cylindrical pin holder 112. A substantially cylindrical coupler pin 111 is supported by the pin holder 112. The coupler pin 111 is axially movable in a direction parallel to the axis of the pivot shaft 109. The pin 111 is urged toward the disk 106 by a spring 115 accommodated in the pin holder 112. One end of the pin 111 is coupled to a limit ring 116.
When the rear window 108 is closed as shown in FIG. 25, the coupler pin 111 enters the coupler hole 106a in the disk 106, which operably couples the crank lever 110 to the disk 106. When the actuator 101 pivots the disk 106, the crank lever 110 pivots integrally with the disk 106. The alternating rotation of the crank level 110 is transmitted to the wiper arm 103 by the pivot shaft 109. Accordingly, the wiper arm 103 pivots in an angle range that corresponds to the angle range of the disk 106, which causes the wiper blade to wipe the surface of the rear window 108.
When the rear window 108 is opened, the coupler pin 111 is separated from the coupler hole 106a, which disengages the crank lever 110 from the pivot disk 106.
When the rear window 108 is opened, the wiper arm 103, the pivot shaft 109 and the crank lever 110 are free to pivot. Thus, if the rear window 108 is closed, the coupler pin 111 on the crank lever 110 may be misaligned with the coupler hole 106a. In this case, the coupler pin 111 contacts the surface of the pivot disk 106 and retracts against the force of the spring 115. However, the pin 111 is located in the path of the hole 106a ,and the hole 106a eventually becomes aligned with the pin 111 when the pivot disk 106 is pivoted by the actuator 101. When aligned with the hole 106a, the pin 111 enters the hole 106a. 
To cause the pin 111 to positively enter the hole 106a, the wiper device of FIGS. 25 to 28 has pair of limit plates 113. The limit plates 113 are fixed to the holder 107 and are spaced apart by a predetermined angular interval to limit the pivot angle range of the crank lever 110 or the range of the pin 111. As shown in FIG. 27, a rubber cushion 114 is fitted about the pin holder 112 to reduce noise that is produced when the pin 111 hits the limit plates 113. The rubber cushion 114 contacts the limit plates 113, which limits the pivot angle range of the crank lever 110 within the pivot angle range X of the hole 106a. Therefore, when the rear window 108 is closed, the pin 111 is always located within the angle range X, or the path, of the hole 106a. 
When the rubber cushion 114 contacts one of the limit plates 113 as shown in FIG. 27, the pin 111 is located within the range X of the hole 106a by a distance B. This is done to prevent the pin 111 from moving outside the range X of the hole 106a. However, the range X of the hole 106a is needed to permit the wiper blade to wipe a sufficient area on the window 108. Therefore, the wiper arm 103 must pivot in the range X of the hole 106a. 
In FIG. 28, the pin 111 is engaged with the hole 106a. The rubber cushion 114 contacts one of the plates 113 and is deformed to permit the hole 106a to move to the end of the range X. Therefore, when the rear window 108 is closed, the crank lever 110 and the wiper arm 103 can be pivoted in a range that corresponds to the range X of the hole 106a. 
However, in the wiper device of FIGS. 25 to 27, the rubber cushion 114 collides with one of the limit plate 113 every time the hole 106a is moved to one of the ends of the range X. This generates noise and can damage the rubber cushion 114 or the limit plates 113.
Accordingly, it is an objective of the present invention to provide a simple and durable vehicle wiper device that securely engages a pivot shaft of a wiper arm with an actuator.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, a wiper device for wiping a window supported by a support is provided. The wiper device is located between the window and the support. The window opens and closes an opening in the support. The device includes an actuator, a first coupler, a pivot shaft, a second coupler, a wiper arm and a guidance structure. The actuator is supported by the support and has an output shaft. The first coupler is attached to the output shaft. The actuator pivots the first coupler in a first angle range. The pivot shaft is rotatably supported by the window. When the window is closed, the axis of the pivot shaft is aligned with the axis of the output shaft. The second coupler is attached to the pivot shaft. When the window is closed and the second coupler is at a predetermined rotational phase relative to the first coupler, the second coupler is coupled to the first coupler to transmit rotation of the output shaft to the pivot shaft. The wiper arm is attached to the pivot shaft. When the actuator is activated with the second coupler coupled to the first coupler, the wiper arm pivots in an angle range corresponding to the first angle range. When the second coupler is outside the first angle range, the guidance structure guides the second coupler to the first angle range by mechanical engagement.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.